In electric power management, it is preferable to efficiently generate power and send power according to a power consumption of a load. For example, Patent Literature 1 discloses a power supply system of a network system comprising a plurality of solar light generated power supply systems connected to a communication line, and an information source device which measures weather information such as an amount of solar radiation, and transmits the weather information to the solar light generated power supply system. With such a structure, a load device can be efficiently driven based on the amount of power generation which is predicted with a high precision.
Patent Literature 2 discloses a monitoring device for power consumption of a utility wherein information is received from a smart meter system and a transceiver, and a power usage status, a power consumption cost, and power consumption rate are visually displayed through a light-emitting display.
When the power consumption of the load changes, the peak electric power may become excessive, and the electric power fees may become expensive, and in addition, a situation may occur in which the supply of electric power cannot handle the peak electric power. An electricity storage device can be used to average the supply and demand of the electric power. As the electricity storage device, a secondary battery such as a lithium ion battery may be used.
Patent Literature 3 discloses a management device of a lithium ion battery wherein a state of charge/discharge of a lithium ion battery is judged based on a measured value of a charge/discharge current of the lithium ion battery, a measured value of the temperature of the battery, and information of supply of electricity of a commercial power supply, and a remaining capacity of the lithium ion battery is calculated.